javascript isalpha – isAlpha. JavaScript, String, Regexp. Use RegExp.prototype.test() to check if the given string matches against the alphabetic regexp pattern.
javascript isalpha – javascript String isalpha() Method
You could just use a case – insensitive regular expression Checks if the character is an alphabetic character.
- /*/^[a-zA-Z()]*$/ – also returns true for an empty string
- /^[a-zA-Z()]$/ – only returns true for single characters.
- /^[a-zA-Z() ]+$/ – also allows spaces*/
- //better regEX to include question marks too
Example
const isAlpha = str => /^[a-zA-Z]*$/.test(str);
isAlpha('pakaInfo'); // true
isAlpha('welcom To pakainfo'); // false
isAlpha('986565'); // false
Check if a character is alphabetic
`a`.isAlpha(); // true `i`.isAlpha(); // true `3`.isAlpha(); // false
Python String isalpha() Method
txt = "pakainfoCom" x = txt.isalpha() print(x)
Don’t Miss : JavaScript Tutorial
isalphabetic javascript
function isAlphaOrParen(str) {
return /^[a-zA-Z()]+$/.test(str);
}
Javascript Function that returns true if a letter?
You can use the String.prototype.match() method along with a regular expression to check if a character is a letter or not in JavaScript. Here’s an example function that returns true if a given character is a letter:
function isLetter(char) {
return char.match(/[a-zA-Z]/);
}
In this function, the match() method checks whether the char parameter matches any of the lowercase or uppercase letters between a-z or A-Z respectively. If it does, it returns an array of matches, which is a truthy value. If it doesn’t match any letter, it returns null, which is a falsy value.
You can use this function to check whether a given character is a letter or not by calling it with the character as the argument. For example:
console.log(isLetter('A')); // true
console.log(isLetter('a')); // true
console.log(isLetter('1')); // false
console.log(isLetter('%')); // false
In this example, the function returns true for the first two calls since ‘A’ and ‘a’ are letters, and false for the last two calls since ‘1’ and ‘%’ are not letters.
Isalpha, isalnum in Javascript?
In JavaScript, there are no built-in functions named isalpha() or isalnum() as they exist in some other programming languages such as Python or C++. However, you can implement similar functionality using regular expressions and the String.prototype.match() method.
isalpha(): This function is used to check if a string contains only alphabetic characters (A-Z, a-z). You can use the following regular expression to achieve this:
function isAlpha(str) {
return /^[a-zA-Z]+$/.test(str);
}
In this function, the ^ and $ characters match the start and end of the string, respectively. The [a-zA-Z] part matches any alphabetic character, and the + character means that the previous pattern should match one or more times. The test() method returns a Boolean indicating whether or not the given string matches the regular expression.
isalnum(): This function is used to check if a string contains only alphanumeric characters (A-Z, a-z, 0-9). You can use the following regular expression to achieve this:
function isAlnum(str) {
return /^[a-zA-Z0-9]+$/.test(str);
}
In this function, the regular expression is similar to the one used in isAlpha(), except that it also includes the digits 0-9 in the pattern.
You can use these functions to check if a string contains only alphabetic or alphanumeric characters, like this:
console.log(isAlpha('HelloWorld')); // true
console.log(isAlpha('Hello123')); // false
console.log(isAlnum('Hello123')); // true
console.log(isAlnum('Hello@123')); // false
In these examples, the functions return true if the given string contains only alphabetic or alphanumeric characters, and false otherwise.
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